Why does the dramatic power of Abraham Lincoln's assassination elude so many filmmakers? No less than D.W. Griffith tried it twice: Both "Birth of a Nation" and "Abraham Lincoln" portrayed the event with decent build-up but very little payoff. A long-gestating adaptation of James L. Swanson's "Manhunt: The 12-Day Chase for Lincoln's Killer" holds potential for freeing the events from historical rigidity. But even 146 years after his death, Lincoln's legacy contains such sacred connotations that filmmakers still shy away from anything but cautious portrayals.

Why does the dramatic power of Abraham Lincoln's assassination elude so many filmmakers? No less than D.W. Griffith tried it twice: Both "Birth of a Nation" and "Abraham Lincoln" portrayed the event with decent build-up but very little payoff. A long-gestating adaptation of James L. Swanson's "Manhunt: The 12-Day Chase for Lincoln's Killer" holds potential for freeing the events from historical rigidity. But even 146 years after his death, Lincoln's legacy contains such sacred connotations that filmmakers still shy away from anything but cautious portrayals.

Now, Robert Redford has returned to the scene of the crime with a stuffy costume drama and the same fastidious allegiance to history. "The Conspirator" opens with a swift recreation of the assassination and then turns to the trial of 42-year-old Mary Surratt (Robin Wright), whose son plotted the assassination with John Wilkes Booth at Surratt's boarding house. The complexities of these morally ambiguous proceedings soon become a dry legal thriller.

The story focuses on conflicted defense attorney Frederick Aiken (James McAvoy), a Civil War hero initially convinced of Surratt's guilt until he becomes her sole defender. James Solomon's screenplay emphasizes Aiken's transition into a principled humanitarian facing down the harsh military tribunal led by Secretary of War Edwin Stanton (Kevin Kline). Aiken, whose post-legal career found him working as a journalist, ascertains the tribunal's motive for indicting Surratt as mainly a form of image control: Unable to capture her son, they refuse to let his spot in the trial go unfilled.

It should be said that "The Conspirator" is reasonably well-acted by a cast that relishes the opportunity to don period costumes and make the setting come to life. The cinematography, by Newton Thomas Sigel ("Valkyrie"), obtains a near-sepia look that distinguishes the era in popular memory. However, while Redford frames the drama with a tense atmosphere, it doesn't shake the sense that we're watching a tame made-for-TV affair.

For a brief moment, in the scenes following the assassination, Redford finds an intriguing angle by staging it as a detective story. But then the rushed exposition arrives, glossing over the hunt for Booth and the subsequent capture of his co-conspirators, and Aiken's case becomes the focus of the straightforward plot.

Redford's last great movie was "Quiz Show," which also dealt with a landmark tale of injustice that took place in the public eye. There, however, he grappled with events on a deeply personal level. "The Conspirator," by comparison, has a rigid, textbook-like feel. As with his last directing credit, 2007's "Lions for Lambs," the extensive debates about civil responsibility veer into didactic territory.

Aiken is a solid hero for a patriotic cause, but that can't save "The Conspirator" from proceedings that lack momentum. It's possible that the only hope for rejuvenating Lincoln on film will come with the upcoming release of "Abraham Lincoln: Vampire Hunter," because Redford's treatment simply sucks the life out of the material.

HOW WILL IT PLAY? Redford's name will raise the movie's profile somewhat, but most audiences won't both with this unimaginative work, which has garnered mixed reviews since its premiere at the Toronto International Film Festival.

criticWIRE grade: C+

Roadside Attractions will release "The Conspirator" nationwide April 15.